Methionine as a novel co-pigment for color stabilization in Dendrobium officinale flower juice: Mechanisms and applications

Abstract

This study systematically evaluated eight amino acids and five organic acids as co-pigments to enhance the color stability of Dendrobium officinale flower juice (DOFJ). Comparative evaluation revealed L-methionine (Met) and caffeic acid as the most effective color stabilizers. At their respective optimal concentrations, Met (0.8 % w/v) demonstrated superior performance than caffeic acid (the anthocyanin-to-caffeic acid ratio of 1:180), significantly reducing color degradation (ΔE < 3.5 after 10 days at 25 °C) and improving anthocyanin retention (50.6 %). Dendrobium officinale flower anthocyanins (DOFA) characterization identified cyanidin-3-O-(6-O-malonyl-glucoside) (47.9 %) and cyanidin-3-O-glucoside (15.3 %) as the major anthocyanins. FT-IR and XRD confirmed hydrogen bonding between Met and DOFA. In addition, differential scanning calorimetry revealed that the incorporation of Met enhanced the thermal stability of DOFA, likely due to the intermolecular interactions between the two components. Molecular docking further demonstrated that the increased stability of Met-DOFA couplings could be attributed to their intermolecular interactions, mainly through hydrogen bonding. Importantly, electronic nose and GC-MS analyses showed that the addition of Met did not adversely affect DOFJ and that the major flavor compounds remained aldehydes, alcohols and alkenes. These results demonstrated Met functionality as a color stabilizer.